Auxiliary coolant tank for exhaust aftertreatment system

ABSTRACT

An auxiliary coolant tank for an exhaust aftertreatment system is provided. The auxiliary coolant tank includes an inlet connection port and an outlet channel. The outlet channel includes a first portion and a second portion. The first portion extends parallel to a plane of a first side and a plane of an upper face. The first portion includes a fluid pick-up port at an end of the first portion. The fluid pick-up port is proximal to a first upper corner. The first portion is connected to the second portion at a location proximal to a second upper corner. The second portion extends parallel to a plane of the third side and the plane of the upper face. The second portion includes an outlet port at an end of the second portion.

TECHNICAL FIELD

The present disclosure relates generally to exhaust aftertreatment systems. More specifically, the present disclosure relates to an auxiliary coolant tank for an exhaust aftertreatment system.

BACKGROUND

Exhaust gases from internal combustion engines may contain substances, such as nitrogen oxides (NOx), particulate matter, and the like, which are unfavorable to the environment. Over the years, efforts have been made within the automotive industry and off-highway industry to reduce the release of unfavorable substances in the exhaust gases. This has been accomplished by modification of the combustion process and by treatment of the exhaust gases before discharge into the atmosphere. One strategy of catalytic reduction of NOx emissions is achieved by use of a selective catalytic reduction (SCR) system, which may include a reductant tank, a reductant injector, and a catalytic chamber. The reductant tank may store a reductant and supply the reductant to the reductant injector for catalytic reduction. The catalytic reduction may involve introduction of a reductant into an exhaust gas stream, by the reductant injector. The reductant may typically be a liquid ammonia source, such as an aqueous urea solution. The reductant injector may be positioned upstream from the catalytic chamber, which may include an SCR catalyst. The SCR catalyst may typically comprise a mixture of catalyst powders, such as titanium oxide, vanadium oxide, and tungsten oxide. During this process, the SCR catalyst facilitates a reaction between the reductant, such as ammonia and NOx, to produce water and nitrogen gas, thereby removing NOx from the exhaust gas.

During operation, the reductant injector may become too hot, which may compromise the reductant injector's performance. Hence, a cooling arrangement may be provided to prevent heat-up of the reductant injector. However, as the engine is keyed off or shut down, the reductant injector may be subjected to heat soak because the coolant flow to the reductant injector ceases. High temperature of the reductant injector may result in localized boiling of coolant in the reductant injector. Localised boiling of the reductant within the coolant passage may result in air pockets that prevent heat dissipation.

One way to prevent overheating of the reductant injector is to use Delayed Engine Shutdown (DES), wherein the engine is kept running for a period of time to allow the coolant flow to the reductant injector after key-off. However, some machine operators may not be comfortable with the use of DES and therefore there is a need for an alternative cooling strategy. An improved cooling arrangement for use of the reductant injector in an exhaust aftertreatment system is desired.

SUMMARY

The present disclosure relates to an exhaust gas aftertreatment system for an internal combustion engine. The exhaust gas aftertreatment system includes at least one selective catalytic reduction (SCR) catalyst and at least one reductant injector. The reductant injector is configured to inject a reductant into the exhaust gas passage downstream from an exhaust portion of the internal combustion engine. The exhaust gas aftertreatment system, further, includes a coolant circuit to cool the reductant injector. The coolant circuit includes a main coolant tank configured to deliver coolant to the reductant injector, and an auxiliary coolant tank in fluid communication with the reductant injector. The auxiliary coolant tank includes an upper face, a lower face and four sides.

According to the present disclosure, the auxiliary coolant tank includes an inlet connection port and an outlet channel. The inlet connection port is structured and arranged in the lower face of the auxiliary coolant tank. The outlet channel includes a first portion and a second portion. The first portion extends parallel to a plane of a first side and a plane of the upper face. The first portion includes a fluid pick-up port at an end of the first portion. The fluid pick-up port is proximal to a first upper corner defined by the first side, a second side, and the upper face. The second portion is connected to the first portion at a location proximal to a second upper corner defined by the first side, the upper face, and a third side opposite to the second side. The second portion extends parallel to a plane of the third side and a plane of the upper face. The second portion includes an outlet port at an end of the second portion.

According to one aspect of the disclosure, the auxiliary coolant tank includes the outlet channel which is L-shaped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic of an engine system, in accordance with the concepts of the present disclosure;

FIG. 2 illustrates an auxiliary coolant tank of an exhaust aftertreatment system in the engine system of FIG. 1, in accordance with the concepts of the present disclosure;

FIG. 3 illustrates a perspective view of the auxiliary coolant tank of FIG. 2, an upper face of the auxiliary coolant tank being removed, to illustrate the structure of coolant exit passage from the tank, in accordance with the concepts of the present disclosure;

FIG. 4 illustrates the auxiliary coolant tank of FIG. 2, in a horizontal orientation, in accordance with the concepts of the present disclosure;

FIG. 5 illustrates the auxiliary coolant tank of FIG. 2, in a clockwise tilted orientation, in accordance with the concepts of the present disclosure; and

FIG. 6 illustrates the auxiliary coolant tank of FIG. 2, in a counter clockwise tilted orientation, in accordance with the concepts of the present disclosure.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown an engine system 100. The engine system 100 may include an engine 102 and an exhaust aftertreatment system 104. The engine 102 may include features not shown, such as fuel systems, air systems, cooling systems, peripheries, drivetrain components, turbochargers, and/or the like. The engine 102 may be any type of engine (internal combustion, turbine, gas, diesel, gaseous fuel, natural gas, propane, and/or the like), may be of any size, with any number of cylinders, and in any configuration (“V,” in-line, radial, and/or the like). The engine 102 may be used to power any machine or other device, which includes: locomotive applications, on-highway trucks or vehicles, off-highway trucks or machines, earth moving equipment, generators, aerospace applications, marine applications, pumps, stationary equipment, and/or other engine powered applications known in the art.

Referring to features shown in FIG. 1, the engine 102 may include a plurality of cylinders 106 and a plurality of exhaust portions 108. The plurality of cylinders 106 are located in the engine 102 and may receive a combination of air and fuel. The air/fuel mixture is combusted in the plurality of cylinders 106. The combustion of the air/fuel mixture produces exhaust gases in the cylinder 106. The exhaust gases from the cylinder 106 flow through the exhaust portions 108, into the exhaust gas aftertreatment system 104.

The exhaust gas aftertreatment system 104 is configured to treat one or more exhaust streams produced by combustion in the cylinders 106 of the engine 102. The exhaust aftertreatment system 104 includes a variety of emission treatment technologies, including, but not limited to: regeneration devices, heat sources, oxidation catalysts, diesel oxidation catalysts (DOCs), diesel particulate filters (DPFs), selective catalytic reduction catalysts (SCRs), lean NOx traps (LNTs), mufflers, or other devices.

The exhaust aftertreatment system 104 may include an exhaust gas passage 110, an SCR module 112, an exhaust outlet 114, an intermediate flow region 116, a reductant system 118, and a controller 120. The exhaust gas passage 110 is located downstream from the exhaust portion 108 and is in fluid communication with the exhaust portion 108. An exhaust gas flow being navigated from the exhaust portion 108, is depicted by arrow 122. The exhaust stream is navigated to the SCR module 112, via the exhaust gas passage 110. A flow of treated exhaust stream which exits the SCR module 112 navigates towards the exhaust outlet 114, is depicted by arrow 124. The SCR module 112 may be a flow-through support body which includes an SCR catalyst 126. The SCR module 112 facilitates continuous passage of the exhaust stream (shown by 122) across the SCR module 112 towards the exhaust outlet 114. The SCR catalyst 126 reduces the NOx emissions by conversion of the NOx emissions in the exhaust gases into diatomic nitrogen (N2) and water (H2O).

The reductant system 118 may include a reductant source 128, a reductant pump 130, a reductant injector 132, and a coolant circuit 134. The reductant system 118 may be configured in a variety of ways. Any system capable of supplying a desired amount of reductant on demand to the exhaust stream may be used. In an exemplary embodiment, the reductant source 128 is a box shaped tank, as shown in FIG. 1. The reductant source 128 may be a tank, vessel, absorbing material, or other device commonly known in the art, capable of storing and releasing the reductant. The reductant may be urea, ammonia, diesel fuel, or some other hydrocarbon used to remove NOx emissions from the exhaust stream. The reductant source 128 is in fluid communication with the reductant injector 132, via the reductant pump 130. The reductant pump 130 may be any extraction device capable of pulling the reductant from the reductant source 128 and delivering the reductant to the reductant injector 132. There may be a valve (not shown) positioned between the reductant source 128 and the reductant injector 132, which is included to regulate or control the delivery of the reductant to the reductant injector 132.

The reductant injector 132 includes a coolant port connection 136 and a coolant outlet port 138, respectively, configured to allow entry and exit of the coolant to the reductant injector 132. However, the reductant injector 132 may include springs, washers, cooling channels, injector pins, and/or other features not shown. The reductant injector 132 is disposed upstream of the intermediate flow region 116. The reductant injector 132 is configured to inject the reductant into the exhaust stream which exits the cylinder 106 and enters the intermediate flow region 116. The intermediate flow region 116 is located upstream from the SCR module 112. In the intermediate flow region 116, the reductant is injected by the reductant injector 132 and hence the reductant mixes with the exhaust stream. The intermediate flow region 116 may include a plurality of structures which enhance disruption of the flow stream of the mixture and/or provide adequate time for the exhaust gas and the reductant to sufficiently mix. A mixture of the reductant and the exhaust stream flows through the intermediate flow region 116 and enters the SCR module 112. In the SCR module 112, the SCR catalyst 126 reduces the NOx emissions by converting the NOx emissions in the exhaust gases into diatomic nitrogen (N2) and water (H2O).

Further, the exhaust aftertreatment system 104 also includes the coolant circuit 134, which may cool the reductant injector 132, in particular the tip portions (not shown) of the reductant injector 132. The coolant circuit 134 includes a main coolant tank 140, a coolant pump 142, an auxiliary coolant tank 144, a first coolant passage 146, a second coolant passage 148, and a third coolant passage 150. The main coolant tank 140 stores the coolant and is fluidly connected to the coolant pump 142, via the first coolant passage 146. The coolant pump 142, powered by the engine 102, is configured to pump the coolant from the main coolant tank 140 to the reductant injector 132. The coolant pump 142 is in fluid communication with the coolant port connection 136 of the reductant injector 132, via the first coolant passage 146. The coolant exits the reductant injector 132 through the coolant outlet port 138. The coolant outlet port 138 is in fluid communication with the auxiliary coolant tank 144, via the second coolant passage 148. The auxiliary coolant tank 144 is fluidly connected to the main coolant tank 140, via the third coolant passage 150, thereby allowing the coolant to flow back to the main coolant tank 140.

In normal operating condition, when the coolant pump 142 is powered by the engine 102, the coolant circulates in the coolant circuit 134 in a counter-clockwise direction. The coolant circulates from the main coolant tank 140 to the reductant injector 132. The hot coolant from the reductant injector 132 flows to the auxiliary coolant tank 144 and circulates back to the main coolant tank 140. In situations when the coolant pump 142 is not operational, the coolant ceases to flow in the coolant passage. At that point, if the reductant injector 132 becomes over-heated and the heat is transferred to the coolant channels (not shown) in the reductant injector 132. Transfer of heat to the coolant channels (not shown) results in boiling and evaporation of the coolant around the reductant injector 132. The vapors of the coolant inside the coolant channels (not shown) rise up and flow towards the auxiliary coolant tank 144, via the second coolant passage 148. Movement of the vapors of the coolant towards the auxiliary coolant tank 144 results in creation of a void, or a low-pressure area, in the coolant channels (not shown) of the reductant injector 132. Hence, the coolant from the auxiliary coolant tank 144 rushes down the second coolant passage 148 and is delivered to the reductant injector 132. The coolant thus delivered circulates in the coolant channels (not shown) of the reductant injector 132, thereby cooling the reductant injector 132.

The exhaust aftertreatment system 104 also includes the controller 120, which is configured to control and monitor the operation of the exhaust aftertreatment system 104. The exhaust aftertreatment system 104 may be in communication with the reductant system 118, via a plurality of communication lines 152. The plurality of communication lines 152 control the reductant pump 130 and the valve (not shown), and monitor the various aspects of the reductant system 118, for example, the amount of the reductant available from the reductant source 128.

Referring to FIG. 2, there is shown the auxiliary coolant tank 144 of the coolant circuit 134 (FIG. 1). The auxiliary coolant tank 144 is positioned above the reductant injector 132 (FIG. 1) in the coolant circuit 134 (FIG. 1). The auxiliary coolant tank 144 is configured to receive the coolant that flows into the reductant injector 132. The auxiliary coolant tank 144 is also configured to retain the coolant as part of coolant circuit 134, despite an angle of installation and/or angle of inclination of machine during various operating conditions. In other words, the disclosed design facilitates retention of a maximum volume of the coolant within the auxiliary coolant tank 144, despite the angle of installation and/or angle of inclination of machine during various operating conditions.

The auxiliary coolant tank 144 includes an upper face 200, a lower face 202, a first side 204, a second side 206, a third side 208, and a fourth side 210. The upper face 200 is positioned opposite to the lower face 202, and parallel to each other at a distance. The first side 204 is adjacent to the second side 206 and the third side 208, and oppositely parallel to the fourth side 210. The upper face 200, the lower face 202, the first side 204, the second side 206, the third side 208, and the fourth side 210 form a closed enclosure, as shown in FIG. 2. The first side 204, along with the second side 206 and the upper side 200 defines a first upper corner 212. Similarly, the first side 204, along with the third side 208 and the upper face 200, defines a second upper corner 214. The auxiliary coolant tank 144 may also include a mounting bracket 216 to facilitate mounting of the auxiliary coolant tank 144.

Referring to FIG. 3, there is shown the auxiliary coolant tank 144 which includes an inlet connection port 300 and an outlet channel 302. The inlet connection port 300 is structured and arranged in the lower face 202 of the auxiliary coolant tank 144. The inlet connection port 300 is configured to allow the heated coolant from the reductant injector 132 to enter the auxiliary coolant tank 144. After engine shut-down, when the coolant flows in the clockwise direction (as shown in FIG. 1), the inlet connection port 300 acts as an outlet for the coolant that flows from the auxiliary coolant tank 144 to the reductant injector 132.

In an embodiment, the outlet channel 302 may be an L-shaped channel. The outlet channel 302 includes a first portion 304 and a second portion 306. The first portion 304 extends parallel to a plane of the first side 204, and a plane of the upper face 200. The first portion 304 includes a fluid pick-up port 308 which is disposed proximal to the first upper corner 212. The fluid pick-up port 308 is referred as a point from where the coolant enters the first portion 304 of the outlet channel 302. The coolant that enters the first portion 304 of the outlet channel 302, flows to the second portion 306. The first portion 304 is in fluid communication with the second portion 306. The second portion 306 is connected to the first portion 304 at a location proximal to the second upper corner 214. The second portion 306 extends in a direction which is both parallel to a plane of the third side 208, and parallel to the plane of the upper face 200. Also, the second portion 306 includes an outlet port 310, disposed at an end of the second portion 306.

Referring to FIG. 4, there is shown a horizontal orientation of the auxiliary coolant tank 144. The volume of the coolant is retained in the auxiliary coolant tank 144 at a first fluid level 400, due to location of the fluid pick-up port 308. A minimum volume of the coolant exits the auxiliary coolant tank 144, via the outlet port 310.

Referring to FIG. 5, there is shown the auxiliary coolant tank 144 in a clockwise tilted orientation. The volume of the coolant is retained in the auxiliary coolant tank 144 at a second fluid level 500, due to location of the outlet port 310. A minimum volume of the coolant exits the auxiliary coolant tank 144, via the outlet port 310, in the clockwise tilted orientation of the auxiliary coolant tank 144.

Referring to FIG. 6, there is shown the auxiliary coolant tank 144 in a counter-clockwise tilted orientation. The maximum volume of the coolant is retained in the auxiliary coolant tank 144 at a third fluid level 600, due to location of the fluid pick-up port 308. A minimum volume of the coolant exits the auxiliary coolant tank 144, via the outlet port 310, in the counter-clockwise tilted orientation of the auxiliary coolant tank 144.

Hence, in the above mentioned configurations of FIGS. 4-6, there is always an amount of the coolant that is retained in the auxiliary coolant tank 144. Referring to FIGS. 4-6, the coolant is retained in the auxiliary coolant tank 144 at the first fluid level 400, the second fluid level 500, and the third fluid level 600, respectively, in the horizontal orientation, the clockwise orientation, and the counter-clockwise orientation, of the auxiliary coolant tank 144.

In the exemplary embodiment, the path of coolant in outlet channel 302 is L-shaped. The path of coolant in outlet channel 302 is not limited to L-shape, but could be of any other shape, including a straight path, such that the outlet port 310 and fluid pick-up port 308 are diagonally opposite to each other and lie in the same plane, along the upper face 200 of the auxiliary coolant tank 144.

INDUSTRIAL APPLICABILITY

The auxiliary coolant tank 144 of the exhaust aftertreatment system 104 is provided. The auxiliary coolant tank 144 retains a reservoir of the coolant despite the angle of installation, and/or inclination of machine at various operating conditions. In other words, the auxiliary coolant tank 144 maximizes the amount of the coolant retained in the auxiliary coolant tank 144 throughout a range of different orientations (such as angles of installation and/or operation) of the auxiliary coolant tank 144. The auxiliary coolant tank 144 provides a natural circulation of the coolant around reductant injector 132, when the engine 102 is in hot-shutdown condition, as the light density vapours tend to move up and the higher density liquid tends to move down.

In operation, atmospheric air may be drawn into the engine 102, mixed with fuel, and then combusted to produce mechanical work. The exhaust gas thus produced from the combustion of the air-fuel mixture may be directed from the engine 102 to the exhaust portion 108. The exhaust stream navigates from the exhaust portion 108 to the exhaust gas passage 110 and then flows to the intermediate flow region 116. From the intermediate flow region 116, the exhaust stream navigates to the SCR module 112. Prior to entry of the exhaust stream into the SCR module 112, the reductant from the reductant injector 132 is introduced into the exhaust stream flowing in the intermediate flow region 116. The exhaust stream flowing through the intermediate flow region 116, has a high temperature. The reductant injector 132 being partially protruded in the intermediate flow region 116, is exposed to the exhaust stream and may get heated due to high temperature of the exhaust stream flowing through the intermediate flow region 116. However, the reductant injector 132 may also heat-up due to injection of the reductant at high injection pressure and due to hot exhaust gasses flowing around reductant injector 132. Hence, the coolant pump 142 is powered by the engine 102 to facilitate cooling of the reductant injector 132.

The coolant pump 142 circulates the coolant to the reductant injector 132 of the exhaust aftertreatment system 104. This cools the reductant injector 132, which may be heated during the operation and injection of the reductant. In normal operating condition, when the coolant pump 142 is powered by the engine 102, the coolant circulates in the coolant circuit 134 in a counter-clockwise direction. The coolant circulates from the main coolant tank 140 to the reductant injector 132, via the first coolant passage 146. The hot coolant exiting from the reductant injector 132 flows to the auxiliary coolant tank 144, via the second coolant passage 148. The coolant retained in the auxiliary coolant tank 144, then circulates back to the main coolant tank 140, via the third coolant passage 150. In some situations, the engine 102 may be keyed off or shutdown and the coolant pump 142 may not be operational. During hot shutdown, the reductant injector 132 is subjected to heat soak because the coolant flow through the reductant injector 132, ceases. The heat soak causes the reductant injector 132 to become hot. The increased temperature of the reductant injector 132 results in localized boiling of the coolant within the reductant injector 132. Due to the localized boiling of the coolant, the coolant evaporates and forms vapors. The vapors of the coolant escape from the reductant injector 132 and moves upwards to the auxiliary coolant tank 144, via the second coolant passage 148. The movement of the vapor of the coolant creates voids or air pockets that prevents heat dissipation from the reductant injector 132 and results in the low pressure regions in the reductant injector 132. The coolant stored in the auxiliary coolant tank 144, towards the reductant injector 132, via the second coolant passage 148, to replenish the void or air pocket. Also, the maximum amount of the coolant is retained inside the auxiliary coolant tank 144, despite the orientation of the auxiliary coolant tank 144. Hence, the coolant is always available to be delivered to the reductant injector 132 from the auxiliary coolant tank 144.

The disclosed auxiliary coolant tank 144 has a combined arrangement and positioning of various elements, such that the auxiliary coolant tank 144 may be oriented in different positions with a minimal amount of the coolant allowed to escape from the outlet port 310 (when there is no pressure). This is useful because the disclosed design of the auxiliary coolant tank 144 may be used with different vehicle engines in different orientations so as to maximize packaging solutions (such as the auxiliary cooling tank need not always be oriented in one position).

It should be understood that the above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure, and the appended claim. 

What is claimed is:
 1. An exhaust gas aftertreatment system for an internal combustion engine, the exhaust gas aftertreatment system including at least one selective catalytic reduction (SCR) catalyst, at least one reductant injector configured to inject a reductant into the exhaust gas passage downstream from the exhaust portion of the internal combustion engine and a coolant circuit to cool the at least one reductant injector, wherein the coolant circuit includes a main coolant tank configured to deliver coolant to the at least one reductant injector and an auxiliary coolant tank in fluid communication with the at least one reductant injector and the main coolant tank, wherein the auxiliary coolant tank having an upper face, a lower face and four sides, the auxiliary coolant tank comprising: an inlet connection port structured and arranged in the lower face of the auxiliary coolant tank; and an outlet channel including: a first portion extending parallel to a plane of a first side and a plane of the upper face, the first portion includes a fluid pick up port at an end of the first portion, wherein the fluid pick up port is proximal to a first upper corner defined by the first side, a second side, and the upper face; and a second portion connected to the first portion at a location proximal to a second upper corner defined by the first side, the upper face, and a third side opposite to the second side, the second portion extends parallel to a plane of the third side and the plane of the upper face, wherein the second portion includes an outlet port at an end of the second portion.
 2. The exhaust gas aftertreatment system according to claim 1, wherein the outlet channel is L-shaped. 